Nosocomial outbreak caused by disinfectant-resistant Serratia marcescens in an adult intensive care unit, Hungary, February to March 2022

In 2022, an outbreak with severe bloodstream infections caused by Serratia marcescens occurred in an adult intensive care unit (ICU) in Hungary. Eight cases, five of whom died, were detected. Initial control measures could not stop the outbreak. We conducted a matched case–control study. In univariable analysis, the cases were more likely to be located around one sink in the ICU and had more medical procedures and medications than the controls, however, the multivariable analysis was not conclusive. Isolates from blood cultures of the cases and the ICU environment were closely related by whole genome sequencing and resistant or tolerant against the quaternary ammonium compound surface disinfectant used in the ICU. Thus, S. marcescens was able to survive in the environment despite regular cleaning and disinfection. The hospital replaced the disinfectant with another one, tightened the cleaning protocol and strengthened hand hygiene compliance among the healthcare workers. Together, these control measures have proved effective to prevent new cases. Our results highlight the importance of multidisciplinary outbreak investigations, including environmental sampling, molecular typing and testing for disinfectant resistance.

Environmental cleaning and disinfection were regulated in a targeted protocol for ICUs in the hospital.The cleaning personnel of ICU-1 was permanent staff.Fluorescent markers were used on a quarterly basis to assess cleanliness.In ICU-1, QAC-SfD was used for the disinfection of surfaces and sinks.The cleaning staff routinely diluted the original concentrate to the manufacturer's recommended concentration using a sensor-based forced-dilution device.The cleaning staff used impregnated, reusable cleaning wipes to clean furniture, equipment and devices.The wipes were impregnated with the QAC-SfD diluted as described above, and taken to the place of cleaning in sealed boxes.After use, the wipes were laundered and then re-impregnated.Until the outbreak, the impregnated wipes had been changed between rooms.Due to the outbreak, the hospital modified the cleaning protocol and requested to change wipes between beds.This supplementary material is hosted by Eurosurveillance as supporting information alongside the article [Nosocomial outbreak caused by disinfectant-resistant Serratia marcescens in an adult intensive care unit, Hungary, February to March 2022], on behalf of the authors, who remain responsible for the accuracy and appropriateness of the content.The same standards for ethics, copyright, attributions and permissions as for the article apply.Supplements are not edited by Eurosurveillance and the journal is not responsible for the maintenance of any links or email addresses provided therein.

Supplementary material 2
Results of positive environmental samples from the intensive care unit 1, associated to the bloodstream-infection outbreak caused by disinfectant-resistant Serratia marcescens in Hungary, February-March 2022.This supplementary material is hosted by Eurosurveillance as supporting information alongside the article [Nosocomial outbreak caused by disinfectant-resistant Serratia marcescens in an adult intensive care unit, Hungary, February to March 2022], on behalf of the authors, who remain responsible for the accuracy and appropriateness of the content.The same standards for ethics, copyright, attributions and permissions as for the article apply.Supplements are not edited by Eurosurveillance and the journal is not responsible for the maintenance of any links or email addresses provided therein.

Supplementary material 3
Number of exposed cases and controls, crude and adjusted matched odds ratios in univariable and multivariable models in an investigation of an outbreak of Serratia marcescens in an intensive care unit, Hungary, February-March 2022 This supplementary material is hosted by Eurosurveillance as supporting information alongside the article [Nosocomial outbreak caused by disinfectant-resistant Serratia marcescens in an adult intensive care unit, Hungary, February to March 2022], on behalf of the authors, who remain responsible for the accuracy and appropriateness of the content.The same standards for ethics, copyright, attributions and permissions as for the article apply.Supplements are not edited by Eurosurveillance and the journal is not responsible for the maintenance of any links or email addresses provided therein.

Supplementary material 4
Results of the comparative genomic analysis of S. marcescens strains isolates from cases and hospital environment in an outbreak investigation in an intensive care unit, Hungary, February-August 2022 Strains were isolated from: HC1-HC8 -blood culture samples of the cases, TRA4 -tracheal tube secretion of case 4 with a S. marcescens different from the outbreak strain, CAN-P1 -cannula of a patient from ICU-1 with a S. marcescens different from the outbreak strain, BW1 and BW2 -bluecoloured, impregnated, reusable cleaning wipe, RB -a red cleaning bucket, GB -a green cleaning bucket.

Comparative results from
a, bMedications to which only controls were exposed are not presented in the table, but the frequency of care variable included these as well.Urinary catheter was not included in the univariable analysis as an exposure variable, as all cases and controls had one, but was included in the frequency of care variable. b